Pyrotechnic devices

ABSTRACT

A pyrotechnic signal device which comprises a discharge tube, a rupturable casing which is housed within the discharge tube and which contains flash-producing composition, and electricallyoperated means for igniting the pyrotechnic composition that includes contacts on the outer surface of the discharge tube.

ilnited States Patent 1191 Murray Dec. 25, 1973 1 PYROTECHNIC DEVHCES[75] Inventor: Dudley Charles Murray,

Homington, near Salisbury, England [73] Assignee: Pains-Wessex Limited,Wiltshire,

England 1221 Filed: June 4,1970

121 AppL No.: 43,483

[52] U.S. Cl l02/37.6, 102/378, 102/70.2 R [51] Int. Cl. C06d 1/04, C06d1/10 [58] Field of Search 102/376, 37.8, 34.4,

[56] References Cited UNITED STATES PATENTS 3,298,311 1/1967 Catlin..lO2/37.8X

2,462,135 2/1949 Skinner 102/702 A 2,977,878 4/1961 Kinkel et al.102/702 A X 3,051,085 8/1962 Finkelstein 102/37.8

Primary ExaminerBenjamin A. Borchelt Assistant Examiner-1ames M. HanleyAtt0rneyHall and Houghton [57] ABSTRACT A pyrotechnic signal devicewhich comprises a discharge tube, a rupturable casing which is housedwithin the discharge tube and which contains flashproducing composition,and electrically-operated means for igniting the pyrotechnic compositionthat includes contacts on the outer surface of the discharge tube.

6 Claims, 1 Drawing Figure Ill] PATENTED 3,780,656

Dumsr 6. MAM/FA 1 INVENTOR ATTORNEY PYao'rEcuNic DEVICES The firing ofthe device results in the production of a flash and a report. Suchdevices can be fired very easily by remote control.

The casing may remain in the discharge tube when the pyrotechniccomposition is combusting so that the composition undergoes combustioninthe discharge tube.

Advantageously, the means for igniting the pyrotechnic compositionincludes an electrical conductor which extends through a compositionwhich ignites when the temperature of the wire is raised by passing asuitable current through the wire, the ends of the electrical conductorbeing connected to the contacts on the outer surface of the dischargetube; this arrangement is particularly reliable in operation.

The contacts are preferably formed on the lower end of the dischargetube, that is, the end of the discharge tube remote from the end throughwhich the casing is projected or a flash emanates. The contacts may bein the form of a printed circuit whose conducting parts comprise acentral portion, and an annular ring surrounding, but spaced apart from,the central portion. Such an arrangement reduces the time taken forconnecting the device to a firing device (that is, to means for applyinga voltage between the contacts), since it is not necessary for thedischarge tube to occupy any particular angular position about the axisof the tubular member when connected to the firing device.

The upper end of the discharge tube may be provided with closure meanswhich are arranged to be displaced or destroyed in response to thefiring of the device, preferably in response to gases of combustiongenerated when the device is fired.

The discharge tube is preferably a cartridge case, for example, astandard 1% inch cartridge case.

Advantageously, the discharge tube is formed of metal and a metal disc(preferably, of aluminum foil) in electrical contact with the wall ofthe discharge tube is positioned in the tube above the casing andextends over substantially the whole of the cross-section of the tube,the disc being arranged to be displaced or destroyed by gases ofcombustion generated when the device is fired. This serves to preventthe electricallyoperated igniting means from being operated accidentallyas is liable to happen with some igniting means in the presence of astrong electric field.

When the pyrotechnic composition is arranged to undergo combustion inthe discharge tube, the casing may be rupturable at its upper end inresponse to combustion of the pyrotechnic composition, so that when thedevice is fired, a flash will emanate from the upper end of thedischarge tube, and the walls of the casing will tend to protect thewalls of the discharge tube from the increase in pressure that occurs oncombustion. The means for igniting the pyrotechnic composition mayinclude an electrical conductor which is connected to the contacts onthe discharge tube, which extends through the lower end of the casing,and which passes through a composition in contact with the pyrotechniccomposition, the composition igniting when the temperature of the wireis raised by passing a current through the wire.

A pyrotechnic signal device, constructed in accor dance with theinvention will now be described in detail, by way of example, withreference to the accompanying drawing, which shows the device in anaxial section.

Referring to the drawing, the signal device comprises an aluminiumdischarge tube in the form of a conventional 1% inch cartridge case,whose upper end is closed by a mill-board disc 23 which is held inposition by lacquer 24. The lacquer 24, which is colored, is used foridentification purposes, as is a disc 25, which is held in position byvarnish 26.

The cartridge case 1 contains a casing which comprises a tube 27 ofrolled Kraft paper closed at the upper and lower ends by end closures inthe form of mill-board discs 28 and 29, which are glued in position. Thetube 27 is secured in the cartridge case 1 by a layer of resinousadhesive (or epoxy adhesive) 31 positioned between the tube 27 and theinner wall of the cartridge case. The casing contains flash-producingpyrotechnic composition 11. The walls of the tube 27 are arranged to bethick enough to protect the wall of the cartridge case when thecomposition 11 undergoes combustion, and the disc 29, which is securedto the base of the cartridge case with an epoxy adhesive, such as theepoxy resin adhesive sold under the trade mark Araldite, similarlyprotects the printed circuit board described hereinafter.

The pyrotechnic composition 11 consists of 42 parts of magnesium powder,8 parts of Acaroid resin, and parts of potassium nitrate, the partsbeing by weight.

The lower end of the cartridge case 1 is recessed to accommodate aprinted circuit consisting of a conductive film comprising a centralportion of conducting material 2 surrounded by an annular ring ofconducting material 3, which are located on a board of insulatingmaterial 4. Wires 5 of an electrically-operated igniting mechanism,indicated generally by the reference numeral 6, pass through a slot 7(or alternatively, they may pass through two holes) formed in the baseof the cartridge case and through holes formed in the printed circuitboard 4 registering with the two parts 2 and 3 of the printed circuit.The wires 5 are soldered to the parts 2 and 3 of the printed circuit, sothat application of a voltage between the two parts of the circuitoperates the igniting mechanism 6.

The head 8 of the igniting mechanism is a conventional electricmatchhead, in which a Nichrome wire is surrounded by a composition whichcombusts when a suitable current passes through the wire. The Nichromewire is connected to the wires 5 of the mechanism. The wires 5 of theigniting mechanism 6 pass through a hole 30 formed in the disc 29 andthe head is located in the pyrotechnic composition 11. The hole 30 issealed with an epoxy adhesive; during the manufacture of the device,when the igniting mechanism 6 has been soldered to the printed circuitboard, the member 27 is inserted in the case 1, epoxy adhesive is spreadaround the base of the igniting mechanism 6 and the slot 7 plugged withit, and the member 29 is inserted in the cartridge case 1 and pushedtowards the base until the adhesive rises up through the hole 30 andseals it.

A thin mill-board disc 32 covered on its lower surface by a layer ofaluminum foil 33 is positioned in the cartridge case ll above the casinghousing the composition Ill. The edges of the aluminum foil 33 areturned around the edges of the disc 32 and the foil makes electricalcontact with the inner wall of the cartridge case 1. In this way,accidental operation of the igniting mechanism 6 due to the presence ofa strong electric field is prevented.

In operation, a suitable voltage is applied between the regions 2 and 3of the printed circuit board, thereby operating the igniting mechanism 6and causing the pyrotechnic composition 11 to ignite. The combustion ofthe composition 11 results in the casing containing it rupturing thediscs 19, 23 and 28 being displaced, and the production of a flash andreport.

I claim:

1. A pyrotechnic signal device comprising a discharge tube of aluminum,one end of said discharge tube being closed and the other end beingopen, a mass of flash-producing composition contained in said dischargetube, a thick-walled rolled paper tube contained in said discharge tube,said paper tube extending between said flash-producing composition andthe side wall of said discharge tube, a thick mill-board disc locatedbetween said flash-producing composition and said closed end of saiddischarge tube, rupturable closure means located between saidflash-producing composition and said open end of said discharge tube toseal in said flash-producing composition, an insulating board secured tothe outside of the said closed end of said discharge tube, a conductivefilm formed on said board on the side remote from said discharge tube,said conductive film including two portions spaced apart from eachother, electrically-operated igniting means located in saidflash-producing composition and having two leads extending therefrom,one of said leads being connected to one of said portions of saidconductive film and the other of said leads being connected to other ofsaid portions of said conductive film, said thick disc and said closedend of said discharge tube having apertures therein, said leadsextending through said apertures, and said apertures being plugged by aresinous adhesive.

2. A pyrotechnic signal device according to claim 1, wherein saidaperture in said closed end of said discharge tube is slot-like andspans said portions of said conductive film.

3. A pyrotechnic signal device according to claim 2, wherein saidinsulating board is secured in a recess in said closed end of saiddischarge tube.

4. A pyrotechnic signal device according to claim 1,

wherein a rupturable closure is provided for said open end of saiddischarge tube, and a metal disc in electrical contact with the sidewall of said discharge tube is positioned in said discharge tube betweensaid electricallyoperated igniting means and said (open end of said)rupturable closure. 5. A pyrotechnic signal device according to claim 1,wherein said closure means seals the end portion of said paper tube thatis adjacent to said open end of said discharge tube, and there isprovided a rupturable closure for said open end of said discharge tube.

6. A pyrotechnic signal device comprising a discharge tube, one end ofsaid discharge tube being closed and the other end being open, a mass offlashproducing composition contained in said discharge tube, ashock-absorbing tube contained in said discharge tube, saidshock-absorbing tube extending between said flash-producing compositionand the side wall of said discharge tube, a layer of resinous adhesivein contact with said shock-absorbing tube and said side wall ofdischarge tube, a shock-absorbing disc located between saidflash-producing composition and said closed end of discharge tube, alayer of resinous adhesive in contact with said shock-absorbing disc andsaid closed end of discharge tube, rupturable closure means locatedbetween said flash-producing composition and said open end of saiddischarge tube to seal in said flash-producing composition, aninsulating board secured to the outside of said closed end of saiddischarge tube, a conductive film formed on said board on the sideremote from said discharge tube, said conductive film including twoportions spaced apart from each other, electrically-operated ignitingmeans located in said flash-producing composition and having two leadsextending therefrom, one of said leads being connected to one of saidportions of said conductive film, and the other of said leads beingconnected to other of said por- Slve.

1. A pyrotechnic signal device comprising a discharge tube of aluminum,one end of said discharge tube being closed and the other end beingopen, a mass of flash-producing composition contained in said dischargetube, a thick-walled rolled paper tube contained in said discharge tube,said paper tube extending between said flash-producing composition andthe side wall of said discharge tube, a thick mill-board disc locatedbetween said flash-producing composition and said closed end of saiddischarge tube, rupturable closure means located between saidflashproducing composition and said open end of said discharge tube toseal in said flash-producing composition, an insulating board secured tothe outside of the said closed end of said discharge tube, a conductivefilm formed on said board on the side remote from said discharge tube,said conductive film including two portions spaced apart from eachother, electrically-operated igniting means located in saidflash-producing composition and having two leads extending therefrom,one of said leads being connected to one of said portions of saidconductive film and the other of said leads being connected to other ofsaid portions of said conductive film, said thick disc and said closedend of said discharge tube having apertures therein, said leadsextending through said apertures, and said apertures being plugged by aresinous adhesive.
 2. A pyrotechnic signal device according to claim 1,wherein said aperture in said closed end of said discharge tube isslot-like and spans said portions of said conductive film.
 3. Apyrotechnic signal device according to claim 2, wherein said insulatingboard is secured in a recess in said closed end of said discharge tube.4. A pyrotechnic signal device according to claim 1, wherein arupturable closure is provided for said open end of said discharge tube,and a metal disc in electrical contact with the side wall of saiddischarge tube is positioned in said discharge tube between saidelectrically-operated igniting means and said (open end of said)rupturable closure.
 5. A pyrotechnic signal device according to claim 1,wherein said closure means seals the end portion of said paper tube thatis adjacent to said open end of said discharge tube, and there isprovided a rupturable closure for said open end of said discharge tube.6. A pyrotechnic signal device comprising a discharge tube, one end ofsaid discharge tube being closed and the other end being open, a mass offlash-producing composition contained in said discharge tube, ashock-absorbing tube contained in said discharge tube, saidshock-absorbing tube extending between said flash-producing compositionand the side wall of said discharge tube, a layer of resinous adhesivein contact with said shock-absorbing tube and said side wall ofdischarge tube, a shock-absorbing disc located between saidflash-producing composition and said closed end of discharge tube, alayer of resinous adhesive in contact with said shock-absorbing disc andsaid closed end of discharge tube, rupturable closure means locatedbetween said flash-producing composition and said open end of saiddischarge tube to seal in said flash-producing composition, aninsulating board secured to the outside of said closed end of saiddischarge tube, a conductive film formed on said board on the sideremote from said discharge tube, said conductive film including twoportions spaced apart from each other, electrically-operated ignitingmeans located in said flash-producing composition and having two leadsextending therefrom, one of said leads being connected to one of saidportions of said conductive film, and the other of said leads beingconnected to other of said portions of said conductive film, saidshock-absorbing disc and said closed end of discharge tube havingapertures therein, said leads extending through said apertures, and saidapertures being plugged by a resinous adhesive.